Ball-point pen tip and ink refill

Abstract

This ball-point pen tip comprises: a holder that is cylindrical in shape, has therein a ball house, and is composed of a swaged part in which the leading end is reduced in diameter toward the inner side; a first tapered face that has a sharp leading end and that is formed on the outer circumference of the holder; a second tapered face that has a sharp leading end, that is formed on the leading end side of the holder as compared with the first tapered face on the outer circumference of the holder, and that has a taper angle which is at least 60° and larger than the taper angle of the first tapered face; a third tapered face that has a sharp leading end, that is formed on the outer circumference of the swaged part, that is contiguous with the second tapered face, and that has a taper angle larger than the taper angle of the second tapered face; and a writing ball that is housed in the ball house in a state of having a portion thereof protruding from the leading end of the holder such that the amount of protrusion from the leading end of the holder is at least 25% of the ball diameter.

Description

Ballpoint pen tips and ink refills

[0001] The present disclosure relates to a ballpoint pen tip and an ink refill for use in a ballpoint pen.

[0002] It is known that in a ballpoint pen tip, a second shoulder portion is provided behind the crimped shoulder portion, and the crimped shoulder portion is positioned outside the imaginary tangent line between the writing ball and the second shoulder portion (see JP 2022-190491 A).

[0003] However, when the writing angle is shallow, the crimped portion of the ballpoint pen tip may come into contact with the paper surface and bend inward.

[0004] The present disclosure aims to provide a technology that can prevent the crimped portion of a ballpoint pen tip from deforming inward during use.

[0005] A first aspect of the present disclosure is a ballpoint pen tip comprising: a cylindrical holder having a ball house therein and constituted by a crimped portion whose tip portion is tapered inward; a tapered first tapered surface formed on the outer periphery of the holder; a tapered second tapered surface formed on the outer periphery of the holder closer to the tip of the holder than the first tapered surface, the second tapered surface having a taper angle of 60° or more that is larger than the taper angle of the first tapered surface; a tapered third tapered surface formed on the outer periphery of the crimped portion, connected to the second tapered surface, and having a taper angle larger than the taper angle of the second tapered surface; and a writing ball that is housed in the ball house with a portion protruding from the tip of the holder, the amount of protrusion from the tip of the holder being 25% or more of the ball diameter.

[0006] A second aspect of the present disclosure is a ballpoint pen tip of the first aspect, wherein, in a virtual cross section including the axis of the holder, the angle of the second tapered surface with respect to a virtual tangent between the writing ball and the boundary between the second tapered surface and the third tapered surface is 20° or less.

[0007] A third aspect of the present disclosure is a ballpoint pen tip of the first or second aspect, wherein, in an imaginary cross section including the axis of the holder, the thickness of the holder from the diameter portion of the writing ball toward the outer periphery when the writing ball is seated in the ball seat of the holder is 16% or more of the ball diameter of the writing ball.

[0008] A fourth aspect of the present disclosure is an ink refill comprising a ballpoint pen tip according to any one of the first to third aspects, and an ink reservoir tube to which the rear end of the ballpoint pen tip is attached and which is filled with ink.

[0009] In addition, the ink refill is an ink refill in which the viscosity of the ink is 1 mPa·sec to 100 mPa·sec.

[0010] According to the present disclosure, it is possible to prevent the crimped portion of the ballpoint pen tip from deforming inward during use.

[0011] FIG. 5 is a front cross-sectional view of a ballpoint pen to which a ballpoint pen tip according to an embodiment of the present disclosure is applied. FIG. 6 is a front cross-sectional view showing a state in which the sealing member has been replaced from the tip front end to the knock portion rear end in the ballpoint pen of FIG. 1. FIG. 7 is a perspective view of a sealing member. FIG. 8 is a front cross-sectional view of an ink refill applied to the ballpoint pen of FIG. 1. FIG. 9 is a front cross-sectional view of a ballpoint pen tip according to an embodiment of the present disclosure applied to the ink refill of FIG. 4. FIG. 5 is an enlarged view of a portion indicated by arrow 6X in FIG. 5. FIG. 6 is a front view of the tip of the ballpoint pen tip shown in FIG. 6. FIG. 7 is a cross-sectional view taken along arrow 8X-8X in FIG. 6. FIG. 8 is an enlarged view of the tip of the ballpoint pen tip shown in FIG. 6 before crimping.

[0012] Hereinafter, embodiments of the present disclosure will be described with reference to the drawings. Components indicated by the same reference numerals in each drawing are identical or similar components. Note that duplicated descriptions and reference numerals may be omitted in the following embodiments. Furthermore, all drawings used in the following description are schematic, and the dimensional relationships and ratios of elements shown in the drawings do not necessarily correspond to the actual ones. Furthermore, the dimensional relationships and ratios of elements between multiple drawings do not necessarily correspond to the actual ones. In the following description, the side of a ballpoint pen where the ballpoint pen tip is located is referred to as the "front end," and the opposite side, i.e., the side where the knock rod (which may also be referred to as the knock button) is located, is referred to as the "rear end." At any position on the ballpoint pen, the direction toward the front end is referred to as the "forward" and the direction toward the rear end is referred to as the "rear."

[0013] 1 and 2 show front cross-sectional views of a ballpoint pen 20 to which a ballpoint pen tip 40 according to an embodiment of the present disclosure is applied. Specifically, the ballpoint pen 20 includes an ink refill 30 (hereinafter, abbreviated as "refill 30" as appropriate) to which the ballpoint pen tip 40 is applied.

[0014] 1, ballpoint pen 20 is a knock-type ballpoint pen. Ballpoint pen 20 includes a barrel body 22, a refill 30 housed in barrel body 22 so as to be movable forward and backward in the axial direction, and a knock mechanism 70 that causes the pen tip of refill 30 to protrude and retract from the tip of barrel body 22.

[0015] Barrel body 22 has a cylindrical barrel 24 that houses refill 30 therein, and a substantially conical tip member 26 that is screwed onto the tip end of barrel 24 .

[0016] A clip member 28 is provided at the rear end portion of the barrel 24 .

[0017] The tip member 26 has an open bottom and a threaded outer circumferential surface, whereby the tip member 26 is attached to the barrel 24.

[0018] [Ink Refill 30] As shown in FIG. 4, the refill 30 includes a ballpoint pen tip 40, an ink reservoir tube 32, and a joint .

[0019] The ballpoint pen tip 40 will be described in detail later.

[0020] The ink containing tube 32 is a tube that contains the ink 31A. In this embodiment, a polypropylene tube is used as an example of the ink containing tube 32. The ink containing tube 32 is filled with ink 31A having a viscosity of, for example, 1 mPa·sec to 100 mPa·sec. Specifically, the viscosity of the ink 31A is 383 sec at a shear rate of 25°C. －１ The viscosity is at 1000 kJ / s. The ink containing tube 32 contains a follower 31B behind the ink 31A.

[0021] The joint 34 is a member for attaching the ballpoint pen tip 40 to the tip of the ink reservoir tube 32. The joint 34 has an ink flow hole formed therein that is smaller in diameter than the press-fit portion for the ballpoint pen tip 40.

[0022] 5 and 6, the ballpoint pen tip 40 is a component that constitutes the refill 30. The rear end of the ballpoint pen tip 40 is attached to the front end of the ink reservoir 32 via a joint 34. Note that the "front end" of the ballpoint pen tip 40 here refers to the side of the ballpoint pen tip 40 that faces the writing front end. The side of the ballpoint pen tip 40 opposite the writing front end is the "rear end."

[0023] 6, the ballpoint pen tip 40 includes a holder 42, a first tapered surface 44, a second tapered surface 46, a third tapered surface 48, and a writing ball 50. The writing ball 50 is seated in a ball seat 58 of the holder 42.

[0024] (Holder 42) The holder 42 constitutes the main body of the ballpoint pen tip 40. The holder 42 is cylindrical and has a ball house 52 inside. Note that the "cylindrical" shape of the holder 42 here refers to a shape in which the internal space is continuous from the front end (one end) 42A to the rear end (the other end) 42B of the holder 42, and there are no particular limitations on the shapes of the inner and outer peripheries.

[0025] The ball house 52 is an internal space formed on the tip 42 A side of the holder 42 to house the writing ball 50 .

[0026] The holder 42 also has a back hole 54. The back hole 54 is an internal space of the holder 42 that extends from the rear end of the holder 42 to the vicinity of the ball house 59. The back hole 54 guides the ink 31A contained in the ink containing tube 32 to the ball house 52.

[0027] A spring (not shown) is inserted into the back hole 54. When the ink refill 30 shown in Figure 4 is used, the writing ball 50 is pressed from the rear end of the holder 42 toward the front end by the spring.

[0028] The holder 42 also has an ink hole 56 between the ball house 52 and the back hole 54. The ink hole 56 is an internal space of the holder 42 that connects the ball house 52 and the back hole 54. The ink hole 56 is a circular hole with a smaller diameter than the back hole 54. A plurality of channel grooves 60 (three in this embodiment), which are grooves that extend in the axial direction of the holder 42, are formed at equal intervals around the ink hole 56 inside the holder 42.

[0029] The ink 31A guided to the tip of the back hole 54 passes from the ink hole 56 through each channel groove 60 and reaches the ball house 52. Note that if the ink 31A used has a relatively high viscosity and is unlikely to cause a direct current, the channel grooves 60 may extend all the way to the back hole 54 from the perspective of the flow of the ink 31A. On the other hand, if the ink 31A used has a relatively low viscosity and is likely to cause a direct current, the channel grooves 60 may stop midway through the ink hole 56, as shown in FIG. 6, rather than extending all the way to the back hole 54.

[0030] The ink 31A that reaches the ball house 52 adheres to the surface of the writing ball 50 and is transferred to the writing surface.

[0031] The holder 42 is also configured with a crimped portion 51, the tip of which is crimped inward to reduce its diameter. Specifically, the tip of the second tapered surface 46 of the holder 42 is crimped radially inward from the pre-crimped state shown in Fig. 9 to the crimped state shown in Fig. 6. The crimped portion 51 has the function of holding the writing ball 50 in the ball house 52 and preventing it from falling out.

[0032] The writing ball 50 inserted into the ball house 52 is pressed backward by a process known as "hammering." A concave surface is formed on the bottom surface of the ball house 52 by transferring part of the curved surface of the writing ball 50. This concave surface is the ball seat 58 (see FIGS. 6 and 8).

[0033] The holder 42 has a rear end portion with a reduced outer diameter, which forms an inserted portion 43. The inserted portion 43 is inserted into the front end of the joint 34, as shown in FIG.

[0034] The holder 42 is formed by cutting a cylindrical metal material such as stainless steel. Depending on the application, the holder 42 may also be formed by plastic deformation and cutting of a pipe material. Preferably, the holder 42 is formed by cutting a cylindrical material made of bismuth-containing ferritic stainless steel, whose Vickers hardness is 270, based on an average measurement of five holders. Bismuth has similar properties to lead (Pb), a commonly used additive for achieving machinability, but its ionization tendency is lower than that of lead. Therefore, it is less likely to leach into ink than lead. Furthermore, unlike harmful lead, it is harmless and has no impact on the environment. The Vickers hardness is preferably between 200 and 450. If the Vickers hardness is below 200, the ball seat 58 will be significantly worn away by the rotation of the writing ball 50 during writing, making it difficult to continue writing for long periods of time. Furthermore, if the Vickers hardness exceeds 450, processing and forming the crimped portion 51 will be difficult. The Vickers hardness was measured at an internal position 0.2 mm from the outer surface of the holder 42 toward the center, and other measurement methods were in accordance with JIS Z2244.

[0035] (First Tapered Surface 44) The first tapered surface 44 is a tapered surface formed on the outer periphery of the holder 42. The taper angle α of the first tapered surface 44 is set to, for example, 25° or more and 35° or less.

[0036] (Second tapered surface 46) The second tapered surface 46 is a tapered surface that is formed on the outer periphery of the holder 42 closer to the tip 42A of the holder 42 than the first tapered surface 44. The taper angle β of the second tapered surface 46 is larger than the taper angle α of the first tapered surface 44. The taper angle β of the second tapered surface 46 is 60° or greater. The taper angle β of the second tapered surface 46 is set, for example, to be greater than or equal to 60° and less than or equal to 80°.

[0037] 6 and 7 , the second tapered surface 46 is connected to the first tapered surface 44, but the present disclosure is not limited to this configuration. For example, one or more other tapered surfaces having a tapered shape may be disposed between the second tapered surface 46 and the first tapered surface 44.

[0038] (Third tapered surface 48) The third tapered surface 48 is a tapered surface formed on the outer periphery of the crimping portion 51. In other words, the third tapered surface 48 is a tapered surface formed on the outer periphery of the tip portion of the holder 42. The third tapered surface 48 is connected to the second tapered surface 46. The taper angle γ of the third tapered surface 48 is larger than the taper angle β of the second tapered surface 44. The taper angle γ of the third tapered surface 48 is set to, for example, not less than 85° and not more than 110°.

[0039] (Writing ball 50) The writing ball 50 is housed in the ball house 52 with a portion of the writing ball protruding from the tip 42A of the holder 42. Specifically, the writing ball 50 housed in the ball house 52 is pressed from the rear end 42B toward the tip 42A by a spring (not shown), so that a portion of the writing ball protrudes from the tip 42A of the holder 42.

[0040] The writing ball 50 is a sphere made of metal, such as ultra-hard stainless steel. The writing ball 50 is preferably formed so that its surface has an arithmetic mean height Sa of 0.06 μm or less. Because the arithmetic mean height Sa of the writing ball 50 surface is 0.06 μm or less, wear of the ball seat 58 caused by rotation of the writing ball 50 can be suppressed. The arithmetic mean height Sa is specified in ISO 25178 and is a value measured using a Taylor Hobson Talysurf CCI Lite with a ball surface measurement range of 50 μm x 50 μm, a measurement magnification of 100 times, and a Gaussian filter of 25 μm.

[0041] The amount H of protrusion of the writing ball 50 from the tip of the holder 42 is 25% or more of the ball diameter D. The amount of protrusion H is set to 25% or more and 45% or less of the ball diameter D.

[0042] As shown in FIG. 6, in an imaginary cross section including the axis C (see FIG. 5) of the holder 42, the angle θ of the second tapered surface 46 with respect to an imaginary tangent L between the writing ball 50 and a second boundary 47 between the second tapered surface 46 and the third tapered surface 48 may be set to 20° or less. The angle θ is set to be greater than 0°. For example, the angle θ may be set to be 8° or greater and 15° or less. The second boundary 47 is the portion of the second tapered surface 46 that has the smallest outer diameter and the portion of the third tapered surface 48 that has the largest outer diameter. The second boundary 47 is sometimes referred to as a crimp shoulder.

[0043] The imaginary cross section including the axis C of the holder 42 is a cross section that is assumed to include the axis C of the holder 42 in the ballpoint pen tip 40 of this embodiment, such as the cross section shown in Fig. 6. The imaginary tangent is a tangent that is assumed to exist between the writing ball 50 and the second boundary 47 in the imaginary cross section.

[0044] In addition, in a virtual cross section including the axis C of the holder 42, when the writing ball 50 is seated in the ball seat 58 of the holder 42, the wall thickness length T on the ball center line CL of the writing ball 50 of the holder 42 may be set to 16% or more of the ball diameter D of the writing ball 50. In addition, the first boundary 45 is the portion where the first tapered surface 44 has the smallest outer diameter and where the second tapered surface 46 has the largest outer diameter.

[0045] As shown in Figure 1, the knock mechanism 70 comprises a coil spring 71 interposed between the barrel body 22 and the ink containing tube 32, a knock portion 72 provided at the rear end of the barrel tube 24, a rotor 74 provided between the knock portion 72 and the refill 30, a plurality of cams 76 protruding from the outer surface of the rotor 74, and a rear tube 80 formed integrally with the clip member 28 and having a plurality of strips 78 protruding from its inner surface.

[0046] The knock portion 72 and the rotor 74 each have a corresponding cam slope, a knock portion cam (not shown), and a knock cam (not shown), respectively. The rotor 74 is configured to rotate in a fixed direction by a predetermined angle when the axial forward knocking action is performed. Furthermore, when the pressure is released after the knocking action, the refill 30 is constantly biased backward by the coil spring 71, and the cam 76 of the rotor 74 and the corresponding rib 78 of the rear barrel 80 rotate the rotor 74 in the same direction as the rotation caused by the knock portion 72 and rotor 74. In other words, the rotor 74 rotates by a predetermined angle, completing one revolution at a certain point (two knocks in the above configuration), and repeats this operation. Furthermore, the tip of the rotor 74 is always in contact with the refill 30, and the front-to-rear position of the cam 76 determines the pen tip position of the tip of the refill 30.

[0047] FIG. 1 shows a cross-sectional view of the ballpoint pen 20 before use. FIG. 2 shows a cross-sectional view of the ballpoint pen 20 in a writing state after use. Before use, a seal member 90, shown in a perspective view in FIG. 3, is press-fitted into the opening at the tip of the barrel at the tip of the ballpoint pen tip 40. This prevents ink from volatilizing when the pen is not in use. After use, the seal member 90 can be attached to the knock bar (operating part) at the rear of the ballpoint pen 20. The seal member 90 is made of a deformable thermoplastic elastomer. When attached to the knock bar, it can cushion the impact when the ballpoint pen 20 is dropped, or, if the ink 31A is thermochromic, can be used as a friction tool that can easily change color with heat.

[0048] Next, the effects of this embodiment will be described. When the third tapered surface 48 contacts the paper surface, stress concentration occurs at the crimped shoulder (second boundary 47), making the crimped portion 51 more likely to deform inward. Therefore, in the ballpoint pen tip 40 of this embodiment, the taper angle β of the second tapered surface 46 is set to 60° or greater. This ensures the thickness of the crimped shoulder, thereby ensuring the rigidity of the crimped portion 51 and suppressing deformation of the crimped shoulder. Furthermore, ensuring the rigidity of the crimped portion 51 increases the ball removal load, improving the effectiveness of preventing the writing ball 50 from falling out. Furthermore, in the ballpoint pen tip 40 of this embodiment, the protrusion amount H of the writing ball 50 from the tip 42A of the holder 42 is set to 25% or greater of the ball diameter D. By setting it in this manner, as shown in FIG. 6, the angle θ of the second tapered surface 46 relative to the imaginary tangent line L can be set within a predetermined range, thereby narrowing the range of writing angles at which the third tapered surface 48 contacts the paper surface. Here, when the third tapered surface 48 comes into contact with the paper surface, stress concentration occurs at the crimped shoulder portion, and therefore the range of writing angles at which the third tapered surface 48 comes into contact with the paper surface is narrowed, thereby suppressing inward deformation of the crimped portion 51 including the third tapered surface 48.

[0049] Furthermore, if the taper angle β of the second tapered surface 46 is less than 60°, the rigidity of the third tapered surface 48 is insufficient, and the effect of suppressing inward deformation of the crimped portion 51 is low. On the other hand, if the taper angle β of the second tapered surface 46 exceeds 80°, the difference with the taper angle γ of the third tapered surface 48 is small, and when the writer looks at the tip of the ballpoint pen tip 40 while writing, the contact point between the writing ball 50 and the paper surface is hidden by the first boundary 45 and is difficult to see, which may make writing difficult or may give the writer the illusion that the writing ball 50 is larger than the actual ball diameter D, resulting in an uncomfortable feeling about the width of the drawn line. Therefore, it is preferable to set the taper angle β of the second tapered surface 46 to be between 60° and 80°.

[0050] Furthermore, if the protrusion amount H of the writing ball 50 is less than 25%, the contact area between the writing ball 50 and the paper surface will be hidden by the first boundary 45 and will be difficult to see. Furthermore, the effect of suppressing inward deformation of the crimped portion 51, including the third tapered surface 48, will be reduced. Furthermore, if the protrusion amount H of the writing ball 50 is 45% or less, the writing ball 50 will be more likely to fall off. Therefore, it is preferable to set the protrusion amount H of the writing ball 50 to between 25% and 45%.

[0051] In the ballpoint pen tip 40 of this embodiment, the angle θ of the second tapered surface 46 with respect to the imaginary tangent line L is set to 20° or less. As a result, as shown in FIG. 6 , the writing angle at which the third tapered surface 48 contacts the paper surface and the writing angle at which the second tapered surface 44 contacts the paper surface are close to each other. In other words, the range of writing angles at which the third tapered surface 48 contacts the paper surface is narrowed. Here, stress concentration occurs at the crimped shoulder when the third tapered surface 48 (around the crimped shoulder of the third tapered surface 48) contacts the paper surface. Therefore, narrowing the range of writing angles at which the third tapered surface 48 contacts the paper surface suppresses inward deformation of the crimped portion 51, including the third tapered surface 48.

[0052] In the ballpoint pen tip 40 of this embodiment, when the writing ball 50 is seated in the ball seat 58 of the holder 42, the thickness length T on the ball center line CL of the writing ball 50 of the holder 42 is set to 16% or more of the ball diameter D of the writing ball 50, thereby improving the effect of suppressing inward deformation of the crimped portion 51.

[0053] In the ink refill 30 of this embodiment, the shear rate of the ink 31A is 383 sec －１ The ink has a viscosity of 1 mPa·sec to 100 mPa·sec at 25°C, which makes writing smooth. In addition, the ink surface tension is set to 20 mN / m to 40 mN / m, which prevents bleeding of handwriting.

[0054] Specific details of the ink preferably include at least a colorant, water, a colorant, and a polyester resin emulsion having a solids concentration of 0.5% to 30% by mass relative to the total amount of the ink composition and a number-average molecular weight (Mn) of 10,000 or more. The polyester resin emulsion can be obtained using at least a polyhydric alcohol component and a polycarboxylic acid component such as a polycarboxylic acid, a polycarboxylic acid anhydride, or a polycarboxylic acid ester. A number-average molecular weight (Mn) of 10,000 or more provides excellent prevention of direct current phenomena and long-term storage stability. The number-average molecular weight (Mn) is a value measured by gel permeation chromatography (GPC) and can be determined, for example, from a calibration curve prepared using a polystyrene standard sample using a Shimadzu Corporation "RID-6A" column (column: Tosoh Corporation "TSK-GEL" column, solvent: tetrahydrofuran (THF), column temperature: 40°C). Examples of commercially available polyester resin emulsions include Elitel KA-0134, Elitel KA-3556, and Elitel KA-6137 manufactured by Unitika Ltd. Alternatively, the ink may contain at least a colorant, water, 0.1% by weight to 30% by weight of an organic solvent based on the total amount of the ink composition, and 0.1% by weight to 30% by weight of a sugar based on the total amount of the ink composition, and the ink composition may contain 0.1% by weight to 30% by weight of an alkylene oxide-adducted glycerin ester, based on the total amount of the ink composition, having a main skeleton of glycerin with a degree of polymerization of 2 to 8, to which 80 moles to 150 moles of ethylene oxide are added, and which is ester-bonded to a fatty acid or aromatic carboxylic acid having 4 to 25 carbon atoms, having an average molecular weight of 2,800 to 10,000 and an HLB of 15 to 19.5, and wherein X is the number of moles of the carboxylic acid-containing substance and Y is the degree of polymerization of glycerin, and the ratio X / [Y+2] is 0.25 to 0.7.

[0055] For the ballpoint pen 20 shown in the above embodiment, the ball diameters D of the writing balls 50 used in the ballpoint pen tip 40 were set to 0.38 mm, 0.5 mm, and 0.7 mm, and the ink 31A was a black ink formulated as shown below, and the refill was made as shown in Figure 4, and the presence or absence of deformation of the crimped portion was measured under the following conditions.

[0056] The ink composition and properties used in the DC test are as follows: Total amount: 100% by mass. Colorant: Colored resin particles (black, solid content 40%: average particle diameter 0.5 μm): 40% Resin: Polyester resin emulsion (Eliteal KA-0134): 5% Resin: Polyester resin emulsion (Eliteal KA-6137): 5% Thickener: Xanthan gum (KELZAN S): 0.3% pH adjuster: Triethanolamine: 0.1% Rust inhibitor: Benzotriazole: 0.3% Preservative: Benzisothiazoline (Biodene 421): 0.3% Lubricant: Phosphate ester (RD-510Y): 0.3% Organic solvent: Glycerin: 10% Water: Distilled water: Rest Ink viscosity: 16 mPa s (using an E-type rotational viscometer [VISCOMETER RE215 (manufactured by Toki Sangyo Co., Ltd.)], cone: 1°34'*R24, measurement time: 60 seconds, shear rate: 383 seconds) －１ , measured in an environment with a measurement temperature of 25°C) Surface tension: 37.4 mN / m (measured in an environment with a measurement temperature of 25°C using a surface tension measuring device: CBVP-Z manufactured by Kyowa Interface Science Co., Ltd.)

[0057] The DC test was performed in an environment of 23±2°C and 65±10% relative humidity. The ballpoint pen barrel (11 g shaft weight) shown in FIG. 2, equipped with an ink refill of each Example or Comparative Example, was dropped downward from a height of 1 m onto a receiving plate inclined at 50° to the horizontal with the writing tip extended. Then, five circles of approximately 20 cm to 25 cm were drawn freehand, and the pen was immediately fixed face-down and left for 60 minutes. The size of the ink droplets accumulated at the tip of the ballpoint pen tip was then measured. The evaluation criteria are as follows: Rating A: No ink droplets; Rating B: Ink droplet size greater than 0 mm and 1 mm or less; Rating C: Ink droplet size greater than 1 mm and 2 mm or less; Rating D: Ink droplet size greater than 2 mm. As shown in Table 1, the Examples were rated A and B, and the Comparative Examples were rated C and D. This confirms that the DC test results of the Examples were better than those of the Comparative Examples.

[0058]

[0059] As a result of measuring whether or not the crimped portion had been deformed, it was confirmed that there was no deformation in the crimped portion in all of the ballpoint pens of the examples.

[0060] The present disclosure can be used in ballpoint pens.

Claims

1. A ballpoint pen tip comprising: a cylindrical holder having an internal ball house and constituted by a crimped portion whose tip portion is tapered inward; a first tapered surface formed on the outer periphery of the holder; a second tapered surface formed on the outer periphery of the holder closer to the tip of the holder than the first tapered surface, the second tapered surface having a taper angle of 60° or more and larger than the taper angle of the first tapered surface; a third tapered surface formed on the outer periphery of the crimped portion, connected to the second tapered surface, and having a taper angle larger than the taper angle of the second tapered surface; and a writing ball contained in the ball house with a portion of it protruding from the tip of the holder, the amount of protrusion from the tip of the holder being 25% or more of the ball diameter.

2. A ballpoint pen tip as described in claim 1, wherein in an imaginary cross section including the axis of the holder, the angle of the second tapered surface with respect to an imaginary tangent between the writing ball and the boundary between the second tapered surface and the third tapered surface is 20° or less.

3. A ballpoint pen tip as described in claim 1, wherein in an imaginary cross section including the axis of the holder, the thickness length of the holder from the diameter portion of the writing ball toward the outer periphery when the writing ball is seated in the ball seat of the holder is 16% or more of the ball diameter of the writing ball.

4. An ink refill comprising: a ballpoint pen tip according to any one of claims 1 to 3; and an ink reservoir tube to the front end of which is attached the rear end of the ballpoint pen tip and which is filled with ink.

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